Yes, it would go to RPI if there is a 3-way tie with each team having three losses. In that case, Bucknell gets the #1 seed since there is no chance at all of LU catching them in RPI. LU would be the 2 seed.
RealtimeRPI often has mistakes. At present, Bucknell’s actual RPI ranking is #80 and LU’s is #107.
BTW, the PL also went to RPI in 2006-07 when Bucknell and Holy Cross tied for 1st with identical 13-1 records.